Epidemiology and costs of surgical treatment of developmental dysplasia of hip in the Brazilian Public Health System in a decade

ABSTRACT Objective: To describe and analyze the epidemiology and costs of surgical treatment of hip dysplasia in the Brazilian Public Health System. Methods: An ecological analytical study that evaluated a time series and the geographic distribution of surgical treatment of hip dysplasia in Brazil. Frequencies of cases, number of cases and associated factors were analyzed. Correlations, frequency maps and flow maps are presented and discussed. Results: During the study, 14,584 patients with dysplasia were admitted to hospitals according to Information Technology Department of the Public Health System. Patients underwent hospital treatment specific for dysplasia in 8,592 cases (at an average cost of R$ 2.225,50, total cost of R$ 19.124.086,25– updated values). In this group, mortality rate was 0.046% and mean hospitalization time was 4.41 days (standard deviation of 2,39 days). Age between 1 and 4 years (37.7%), female sex (64.5%) and white race (46%) were more frequent. Greater rates of specialists (R²=0.82; p<0.001), greater proportion of counties with high/very high human development index (R²=0.79; p<0.001), and higher per capita income (R²=0.68; p<0.001) correlated to greater rates of treatments undertaken per 1,000 live births (as per State of treatment). The factor most related to treatment rate per 1,000 live births (as per State of residence) was white race (R²=0.90; p<0.001). Southern states had higher treatment rates (as per State of residence, rate of 0.73/1,000), and Southeast states had greater absolute frequency of cases (46.7%) and greater flow of patients. Conclusion: The surgical treatment of hip dysplasia in Brazil occurs frequently, at relevant costs, and is distributed in a heterogenous and unequal fashion in the Public Health System. Southern states have a higher incidence of cases, and there is an association with racial and socioeconomic factors. There was no large variation in the incidence of cases over time.


❚ INTRODUCTION
Developmental dysplasia of the hip (DDH) is a condition in which the femoral head has an abnormal relation with the acetabulum, and its severity ranges from cases of instability at birth to dislocation. (1) In the absence of diagnosis or late diagnosis (after the first months of life), treatment becomes more complex, morbidity increases, and the chances of normal development of the hip decrease. (2,3) Therefore, it is an established risk factor for early hip osteoarthritis (before 50 years of age), and a condition of major economic and social impact. (4) In a recent study carried out in a teaching hospital in Brazil, a significant knowledge gap was detected among pediatricians and pediatric residents, who are responsible for clinical triage, and the consequent early referral of patients for treatment. (5) In other countries, strategies such as systematic ultrasonography have been implemented to prevent these cases from not being identified at the ideal time. (6) However, the costeffectiveness of this strategy has been questioned, and this type of screening only seems to be appropriate in places where the prevalence of surgery is high. (7,8) In Brazil, this prevalence does not seem to have been studied yet.
In fact, epidemiological data on this disease vary by geographic region. (9) The incidence of DDH is estimated to be 1.5 to 20 per 1,000 live births, and is four to eight times more prevalent in women. (3,5) There is significant variability in incidence among racial groups in the same geographic location. The incidence of clinical neonatal hip instability at birth ranges, for example, from 0.4 per one thousand in Africans, to 61.7 per thousand in Polish Caucasians. (9) In Brazil, Puech was the pioneer in discussing the epidemiology of DDH. He argued that in our country, at the beginning of the 20 th century, there was a low frequency of this disease, which changed due to migratory currents, mainly from Europe. (10,11) However, no studies have been identified in the last decade exploring the epidemiology of DDH and its treatment.
The null hypothesis of this study is the incidence of surgical treatment of DDH in the Public Health System (SUS -Sistema Único de Saúde) has a frequency similar to that of other countries, does not vary over the years, and is distributed non-uniformly across the states.

❚ OBJECTIVE
To describe and analyze the epidemiology and costs of surgical treatment of hip dysplasia in the Public Health System. einstein (São Paulo). 2021;19:1-11 The data files were obtained from the DATASUS platform, including the entire database of the Hospital Information System of SUS (SIHSUS System), (12) the population base (with data from the 2015 Brazilian population estimate), (13) surveys and research National Household Sample Survey (PNAD -Pesquisa Nacional por Amostra de Domicílios), (14) and the database of the Live Births Information System (SINASC -Sistema de Informações sobre Nascidos Vivos). (15) The data were tabulated and analyzed in the TabWin 4.1.5 software and presented as graphs, tables, and maps. In parallel, we used the 2015 Brazilian medical demography survey, (16) and the registers of specialists of the Brazilian Hip Society (SBQ -Sociedade Brasileira de Quadril) and the Brazilian Society of Pediatric Orthopedics (SBOP -Sociedade Brasileira de Ortopedia Pediátrica), which contain quantitative data with the number of specialists in these surgeries, by geographical unit. (17,18) The study included all the data from the Hospital Admission Authorizations (AIH -Autorização de Internação Hospitalar) performed at SUS, from January 2008 to December 2017.
Among the AIHs included in the study, cases in which there was late treatment of DDH were selected. For this, different selections were made in the parameters of the TabWin software, generating Groups A, B and C.
Group A included all inpatients whose main diagnosis field contained the code Q65 of the International Classification of Diseases and Related Health Problems (ICD-10), which refers to developmental dysplasia of the hip. This parameter aimed to promote a broad search, with good sensitivity for conditions related to diagnosis of dysplasia, although it allowed the inclusion of several cases not necessarily related to late inpatient (surgical) treatment of DDH.
In Group B, an additional filter was included to restrict the cases obtained in the selection of Group A, improving the specificity of the search. The filter consisted of 11 surgical treatments typical of late treatment of DDH with the following SUS codes: 0408040327, 0408060190, 0408040181, 0408040343, 0415010012, 0408040157, 0408040173, 0408040220, 0415020034, 0408040165, and 0415020069, according to the Table of Procedures, Medicines, Orthoses, Prostheses, and Special Materials of the SUS.
In Group C, to remove cases not related to hip sparing surgeries, all cases of patients aged 40 years or older were excluded.
The cases included in Group C made up the final research sample, which was used for all comparisons and analyses. The outcome variables were the annual absolute frequencies and rates of treatments performed per 1,000 live births during the period. Data were tabulated and presented by state and geographic region of treatment and patient residence. The following variables were also evaluated to explore associations: patient age, sex, race, demographic variables (live birth rate, resident population, and per capita household income), as well as health care variables (ratio of hospitals with inpatient care per 100,000 inhabitants). Additionally, also included were ratio of medical schools per 100,000 inhabitants, ratio of SBQ and SBOP specialists per 1 million inhabitants, total hospital costs, and costs per admission.
The data were presented as descriptive statistics by year (incidence rates, percentages, means, and standard deviations -SD). To study associations, the rate of surgical treatments performed per one thousand live births, per state, was calculated and bivariate correlation tables were used, using Pearson's correlation coefficient, with significance level set at 0.05. Statistical tests were performed in the (SPSS) program, version 21.
The geographical distribution of treatments is presented by means of maps generated from the data plotted in TabWin software (version 4.1.5).

❚ RESULTS
From January 2008 to December 2017, a total of 14,584 hospitalizations of patients with a primary diagnosis of hip dysplasia (ICD-10 Q65) were recorded in Brazil at SUS (Group A). We found 68 different types of treatments performed among these patients, many of which were unrelated to the object of this study (for example, cesarean delivery, conservative treatment of fractures, and surgical treatment of polytrauma patients, among others). Table 1 shows the frequency of all treatments performed in Group A and the frequency found in Group B, after applying the treatment filter.
For Group B, we used ICD and treatment code as filters, obtaining an absolute frequency of 9,470 cases treated in a decade. In this group, 22 deaths were recorded (mortality of 0.23%), and the mean hospital stay was 5.07 days (minimum of 1.5 and maximum of 9.95 days). Group Table 2 shows the time progression of treatment frequencies and costs in Group C. A mean of 947 cases were performed per year (SD=85.80). The trend line for Group C shows an increase by less than 10% in the number of treatments over the decade. In addition, Table 2 also shows other frequency and cost data in Group C. Females were the most frequent (64.5% in Group C). The mean age at hospitalization was 8.14 years (SD=7.63 years). The distribution of costs by age group followed a distribution similar to that of frequency (R 2 =0.99). The over-14 years age group, which corresponds to the period of the closure of physis of the triradiate cartilage in the acetabulum and the initial age for the indication of a specific surgery (the Bernese periacetabular osteotomy), accounted for 12.8% of total hospitalization costs (R$ 1.652.459,56). The white race was the most frequent (45.69%), although in many cases (35.84%) the race/color was omitted from the AIH record.
The map in figure 1 shows the absolute frequency of treatments performed per state, according to the place of performance in Group C. Figure 2 demonstrates the mean cost per treatment in each state of treatment surgery in Group C, and the proportional circles indicate the total value of  (15) The proportional circles indicate the total value of hospitalizations by state. hospitalizations in each of them. Interestingly, there was a low correlation between the costs per hospitalization and the frequency of treatment per state (R 2 =0.32); some states with low frequency of treatment had high mean hospitalization costs, such as Rio Grande do Norte and Goiás.
During the study period, the rate of surgical treatment per 1,000 live births was, on average, 0.29 per year in Brazil. Regionally, the highest rate of cases performed and originated in the South Region (0.72/1,000 live births, for both rates) and the lowest in the North (0.05 and 0.09/1,000 live births, respectively), as detailed on table 3.  (15) A correlation analysis by state showed the factors statistically most associated with the rate of surgical cases of DDH per thousand live births in Group C by state of residence were the proportion of white inhabitants (R²=0.90; p<0.001), the Gini index (R²=-0.80, p<0.001), the proportion of municipalities with high or very high Human Development Index (HDI) (R²=0.69, p<0.001), the number of specialists from SBQ and SBOP (R²=0.75, p<0.001), and the per capita income (R²=0.52, p<0.001).
When the association between the same factors and the rate of surgical cases of DDH per one thousand live births was explored in Group C by state, the correlation with white race (R²=0.88) and Gini index (R²=-0.68) decreased. The factors related to care and economic status increased (proportion of municipalities with high or very high HDI, with R²=0.79 and p<0.001; number of SBQ and SBOP specialists, with R²=0.82 and p<0.001); and per capita income, with R²=0.68 and p<0.001) ( Table 4).
The rate of treatments per one thousand live births (by state of residence) is shown in figure 3. The proportional circles indicate absolute frequency of treatments, according to residence of patient. The highest rate was found in the State of Santa Catarina with 0.914 cases per one thousand live births, and the lowest in Amapá, with 0.037 cases per one thousand live births. Figure 4 shows the geographical distribution of cases treated in Group C in absolute numbers (by states where surgery was performed) and the flow of patients between states and regions. It is possible to observe that the Southeast Region absorbed the largest number of patients from other regions, and that proportionally, the states of Rio de Janeiro and Maranhão, as well as the Federal District, treated the most patients from other states. We also identified several flows that crossed the boundaries of large geographic regions. Furthermore, 333 case flows between states were registered in the period, the largest between Minas Gerais and São Paulo (85 cases) and between Goiás and the Federal District (69 cases).     (16) The colors on the map represent the absolute frequency of treatments for developmental dysplasia of the hip in Group C, by state of performance. The proportional circles demonstrate the absolute frequencies of cases performed in each state and the dark slices, the proportion of cases imported from other states. The lines demonstrate the dominant flow of patients between states, and their width is proportional to the number of patients.

❚ DISCUSSION
In some countries, the prevalence of surgical treatment for DDH has been reported to range from 0.7 to 1.3 per 1,000 live births. (19) This value seems to be influenced by the screening strategy to identify early cases (with or without ultrasonography), by hereditary and racial factors. (19,20) A study evaluating the prevalence of surgical interventions in DDH (acetabuloplasty, osteotomy, triple osteotomy, periacetabular osteotomy) in patients born in Austria, Germany, and the Czech Republic from 1992 to 2008 reported a 46% reduction over a 16-year period. (19) In that study, the routine use of screening ultrasound examination was implicated in the decreased need for this type of surgical approach. (19) A rate of 0.29 cases of operated DDH per 1,000 live births was found in our country (ranging from 0.72 to 0.05, depending on the region), which is lower than that reported in the literature. (19) This lower frequency of treatment deserves discussion. First, this study did not include surgeries performed in the private services, which may underestimate the real frequency of treatments performed in Brazil, where about 25.6% of population (2015 data) had access to health insurance plans. The heterogeneous geographic distribution seen in this study confirms the hypothesis initially postulated by Puech, (11) that racial and demographic factors impact on epidemiology of the disease. The Southern Region of the country, which has a large proportion of European migrants, had a treatment rate for DDH more than twice the national average and 15-fold higher than that of the Northern Region. In fact, a nationwide genetic study found a prevalence of up to 85% of European ancestry in some municipalities of that region. (21) The strong correlation between the incidence of surgeries and the proportion of white individuals in the states verified in this study, reinforces the impression that part of this correlation is related to hereditary factors.
However, other factors seem to influence this distribution. Since the study did not directly measure the prevalence of the disease, but that of treatment of a complication of the disease, findings may be related to inequities in access to diagnosis and treatment. Regions with smaller healthcare facilities (lower rate of specialists) and lower socioeconomic indices (income per capita and HDI) have lower rates of cases. In addition, the Southern and Southeastern states received the greatest flow of patients, which increased the polarization of case performance in these centers. In fact, this finding reflects a violation of the SUS principles, whose hierarchical organization presupposes that this type of treatment, in most cases, could be offered at the state level or at most, regional level. The logic of treatment away from home overloads the large centers, generates indirect costs, hinders regional development, discourages the establishment of specialized professionals in inland, and hurts the principle of decentralization of the SUS. In addition, it generates suffering for families who need to travel, in some cases, thousands of kilometers with their small children to receive the appropriate treatment. (22) The literature indicates a four to eight times higher prevalence of DDH in women. (3,5,23) In this study, females corresponded to 67.8% of cases, confirming their predominance in Brazil. This contrasts to a series of cases previously published in Brazil, which reported a higher prevalence in males. (10) When analyzing the results obtained in relation to the racial distribution of DDH surgery, a clear predominance of the white race (42.06%) is observed. This has been reported in other studies in our country, although with different proportions. In a national study, a predominance of the white race was found with a frequency of 81% of cases. (10) This difference may be related to the incomplete filling out of AIHs in Brazil, since in 41.6% of cases included in this study, there was no information regarding the patient's race.
Surgical treatment of DDH is most prevalent among children aged 1 to 4 years in our setting. This is compatible with the most common age range for the indication of surgical treatment of neglected DDH. (9) Considering the reports in the literature that for every 100 cases of DDH, 19 progress to surgery, (19) it is possible to estimate a Brazilian incidence of DDH of 1.52 per one thousand live births (ranging from 3.78 to 0.26 per one thousand live births per region, the highest in Santa Catarina). This means that the estimated incidence of DDH cases in Brazil is lower than that of Mediterranean and Eastern European countries, Japan, Australia, and New Zealand, and higher than some African and Western European countries, besides maintaining similarity with some states in the United States and other South American countries, such as Chile. (24) The differences found in the frequencies of treatments in different groups (search strategies), although revealing different specificities of each search parameter, also led us to discuss the importance of the correct completion of the AIH. Since the information in this study derives from secondary data, factors that influence the filling out and recording of AIHs can einstein (São Paulo). 2021;19:1-11 interfere with the results. Among these factors, the literature mentions the completeness and correctness of the information filled out by the physician; difficulty in deciphering the physician's handwriting; lack of training, and lack of knowledge of the coding rules on the part of hospital employees. (25) An example of this situation was observed in this study, in which the race of the patients was not documented in more than 40% of cases.
There are limitations to this study. This is an ecological study, there is no claim to show causal relations, but simply to analyze associated factors. However, by exploring a robust nationwide database, this study brings to light new information regarding the Brazilian epidemiology of DDH and its complications, in which individual impact on the health of patients and their families can be devastating. A potential bias is related to the quality of the original AIH. The use of three different search strategies (Groups A, B, and C) allowed us to select data more specific to the research object. However, it is not possible to identify all cases of completion errors, omissions, or fraud. In addition to the original information contained in this study, it can help make physicians aware of the importance of feeding the official databases, filling out the HIA correctly, and providing reliable epidemiological information.

❚ CONCLUSION
The frequent surgical treatment of developmental dysplasia of the hip in Brazil generates relevant costs. It is distributed heterogeneously and unevenly throughout the Public Health System. Southern states have the highest incidence of cases. Racial and socioeconomic factors are associated with this distribution. There was a small temporal variation in the incidence of operated cases in the period of a decade.

❚ AUTHORS' CONTRIBUTION
Bruno Gonçalves Schröder e Souza: prepared the research project, compiled and analyzed data, and wrote the manuscript. Bruno Marinho Coelho Vasconcelos and Higor Pereira Pujoni: compiled data and participated in analysis of information. Mário Círio Nogueira: organized the tables, prepared flow maps and participated in analysis of information. Valdeci Manoel de Oliveira and Alfredo Chaoubah: supervised the research, corrected the project and final manuscript, assisted in developing the study design. Moreover, Alfredo Chaoubah: supervised the statistical analysis of data.